It's good fun for about 20 hours. If you play it solo, you'll get a genuinely suspenseful survival horror experience. If you play it in co-op, you can have some fun beating up zombies. The atmosphere is great either way and the locational damage system is the best I've seen. Dismembering and/or crippling zombies has never been so satisfying.

I just bought a few copies of Killing Floor for beating up zombies - hopefully it was worth $5/copy for some coop w/ the family.